Seafloor spreading is a geologic procedure in which tectonic plates—large slabs the Earth"s lithosphere—split personal from each other.
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Seafloor dispersing is a geologic procedure in i beg your pardon tectonic plates—large slabs that Earth"s lithosphere—split personal from every other.
Seafloor spreading and other tectonic activityprocesses are the an outcome of mantle convection. Mantle convection is the slow, churning movement of Earth’s mantle. Convection currents carry heat native the lower mantle and core come the lithosphere. Convection currents additionally “recycle” lithospheric materials earlier to the mantle.
Seafloor dispersing occurs in ~ divergent key boundaries. As tectonic plates slowly move away from each other, warmth from the mantle’s convection currents provides the crust more plastic and also less dense. The less-dense material rises, often forming a hill or elevated area of the seafloor.
Eventually, the crust cracks. Hot magma fueled by mantle convection bubbles as much as fill these fractures and spills top top the crust. This bubbled-up magma is cooled through frigid seawater to kind igneous rock. This absent (basalt) becomes a new part of Earth’s crust.
Seafloor dispersing occurs along mid-ocean ridges—large hill ranges climbing from the ocean floor. The Mid-Atlantic Ridge, for instance, separates the phibìc American plate from the Eurasian plate, and also the southern American plate indigenous the african plate. The eastern Pacific climb is a mid-ocean ridge the runs with the east Pacific Ocean and also separates the Pacific plate native the north American plate, the Cocos plate, the Nazca plate, and also the Antarctic plate. The south east Indian Ridge marks wherein the southern Indo-Australian plate develops a divergent boundary with the Antarctic plate.
Seafloor spreading is not constant at all mid-ocean ridges. Slowly spreading ridges space the sites of tall, narrow underwater cliffs and also mountains. Quickly spreading ridges have actually a much more gentle slopes.
The Mid-Atlantic Ridge, because that instance, is a sluggish spreading center. It diffusion 2-5 centimeters (.8-2 inches) every year and forms an ocean trench around the size of the cool Canyon. The eastern Pacific Rise, on the various other hand, is a fast spreading center. That spreads around 6-16 centimeters (3-6 inches) every year. There is not an s trench in ~ the east Pacific Rise, because the seafloor dispersing is too fast for one come develop!
The newest, thinnest late on earth is situated near the center of mid-ocean ridge—the actual site of seafloor spreading. The age, density, and also thickness of oceanic crust rises with distance from the mid-ocean ridge.
The magnetism of mid-ocean ridges helped scientists very first identify the procedure of seafloor dispersing in the early 20th century. Basalt, the once-molten rock that provides up most new oceanic crust, is a relatively magnetic substance, and also scientists started using magnetometers to measure the magnetism of the s floor in the 1950s. What they found was that the magnetism the the s floor about mid-ocean ridges was separated into equivalent “stripes” ~ above either next of the ridge. The particular magnetism that basalt absent is figured out by the Earth’s magnetic field when the magma is cooling.
Scientists established that the same procedure formed the perfectly symmetrical stripes on both next of a mid-ocean ridge. The continual process of seafloor dispersing separated the stripes in an orderly pattern.
Oceanic crust slowly moves away from mid-ocean ridges and also sites of seafloor spreading. Together it moves, it i do not care cooler, more dense, and more thick. Eventually, larger oceanic tardy encounters a tectonic boundary with continental crust.
In part cases, oceanic crust encounters an active plate margin. An active plate margin is one actual key boundary, whereby oceanic crust and also continental late crash into each other. Energetic plate spare part are often the site of earthquakes and volcanoes. Oceanic crust developed by seafloor dispersing in the east Pacific Rise, because that instance, might become component of the Ring the Fire, the horseshoe-shaped sample of volcanoes and earthquake zones approximately the Pacific s basin.
In other cases, oceanic crust encounters a passive key margin. Passive margins are not key boundaries, but locations where a solitary tectonic bowl transitions native oceanic lithosphere to continent lithosphere. Passive margins room not sites of faults or subduction zones. Special layers of sediment overlay the transitional crust of a passive margin. The oceanic late of the Mid-Atlantic Ridge, for instance, will certainly either become component of the passive margin on the phibìc American bowl (on the east coastline of phibìc America) or the Eurasian key (on the west coastline of Europe).
New geographic attributes can be created through seafloor spreading. The Red Sea, because that example, was created as the african plate and also the Arabian bowl tore far from each other. Today, just the Sinai Peninsula connects the Middle east (Asia) with North Africa. Eventually, geologists predict, seafloor spreading will completely separate the two continents—and join the Red and also Mediterranean Seas.
Mid-ocean ridges and seafloor spreading can also influence sea levels. As oceanic tardy moves far from the shallow mid-ocean ridges, that cools and sinks together it becomes much more dense. This increases the volume that the s basin and also decreases the sea level. Because that instance, a mid-ocean ridge system in Panthalassa—an old ocean that surrounding the supercontinent Pangaea—contributed to shallower oceans and greater sea level in the Paleozoic era. Panthalassa to be an early kind of the Pacific Ocean, which today experiences less seafloor spreading and also has a much less comprehensive mid-ocean ridge system. This helps describe why sea levels have fallen dramatically over the previous 80 million years.
Seafloor spreading disproves one early part of the concept of continental drift. Supporters of continent drift initially theorized the the continents moved (drifted) with unmoving oceans. Seafloor dispersing proves the the s itself is a website of tectonic activity.
Seafloor spreading is simply one component of key tectonics. Subduction is another. Subduction happens where tectonic key crash right into each other instead of dispersing apart. At subduction zones, the leaf of the denser bowl subducts, or slides, in ~ the less-dense one. The denser lithospheric material then melts earlier into the Earth"s mantle.
Seafloor dispersing creates brand-new crust. Subduction destroys old crust. The 2 forces approximately balance each other, so the shape and diameter the the planet remain constant.
Earth"s newest late is produced at web page of seafloor spreading—red website on this map.
Map courtesy NOAA
Seafloor spreading and rift valleys are typical features in ~ “triple junctions.” Triple junctions space the intersection of three divergent plate boundaries. The triple junction is the main point where three cracks (boundaries) split off at around 120° angles from each other.
In the Afar Triple Junction, the African, Somali, and Arabian plates are splitting from every other. The great Rift Valley and Red Sea (a major site of seafloor spreading) space the an outcome of plate tectonics in the Afar Triple Junction.
area where 2 or more tectonic key are moving away from each other. Also called one extensional boundary.
the suddenly shaking of Earth"s crust resulted in by the relax of power along fault lines or from volcanic activity.
mid-ocean ridge wherein seafloor spreading is occuring at more than 100 millimeters (4 inches) a year.
scientific instrument provided to measure up the presence, strength, and also direction the Earth"s magnetic field.
slow motion of Earth"s solid mantle brought about by convection currents transferring warm from the interior of the planet to the surface.
lithospheric an ar where oceanic crust transitions to continent crust there is no faults or subduction zones.
base level because that measuring elevations. Sea level is determined by dimensions taken end a 19-year cycle.
movement of tectonic plates leading to geologic activity such together volcanic eruptions and also earthquakes.
massive slab of heavy rock made up of Earth"s lithosphere (crust and upper mantle). Also called lithospheric plate.
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an opening in the Earth"s crust, with which lava, ash, and gases erupt, and likewise the cone built by eruptions.
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